Spirit level



March 30 I926.

v S. WESTON,

SPIRIT maven Filed August 20, 1923 Patented Mari 30, 1926.

SAMUEL wns'romor LONDON, ENGLANDQASVSIGNOR'IO n it wa'rrs & son, LIMITED,

or LONDON, ENGLAND.

srmrr LE EL.

Application filed August 20, 1923. Serial'li'o. 658,322.

To all whom it may concern:

' Be it known that I; SAMUEL subject of the King of Great Britain, residing at 123 Cainliei-Well Road, in the county of London, England, have invented certain new and useful Improvements in or Relating to Spirit Lei 'elspo't which the following is a specification.

This invention relates to spirit levels having' an air gas or vapour bubble. In such levels it is found that the length of the bubble alters at different atmospheric tern eratures owing to variations in the volume of the bubble as a result of increase or decrease of the volume of the liquid. With lar e temperature variations the alterations b 1n the. length of the bubble are so pronounced as to cause diliiculty in obtaining.

accurate readings. v V 1 According to the present invention 'pro vision is made whereby the lengtlrot the air bubble will remain approximately constant despite temperature variations, by. so ;.for'm ing the interior of-the liquid chamber that when, as a result of variations or temperature, the volume of air (or of theg'as or vapour) is altered, this alteration operates to vary the cross-sectional area of the bubble in such a manner as to inaintainits length constant or approximately so. rise of temperature leads to iZWO separate but simultaneously occurring elfects', vii: (1) expansion of the liquid and consequent diminution in the volume of the hubbleboth in respect to length.and-cross-sectional area,

and (2) decrease of surface tension result ing in decrease of the cross=sectional area or the bubble and increase in its length I owing to the fact that the bubble is situated under a'eurvedsurtace having a re tively' small radius of transverse curvature, the

volume remaining substantially constantso tar as this COIlSltlGilltlOllfllOl'lG 1s concerned. The amount of dm'unution in the volume oi the bubble due to expansion ot the liquid for" a given rise in temperature Wlll obviously depend upon the proportion existing between the volume of liquid and the volume of. air (or of gas or vapour) the diminution increasing as the proportion of liquid to air increases. Bysuitaloly arranging this proportion, a condition of affairs is obtained'in which the decrease in the length of the hubble due to the diminution in volume of the ViTnsToN, a

Apparently, a

air as a result ot' expansion of the liquidis nullified bythe increase nlength due to the decrease in surface tension, the result therefore being that the'buh ole is lnail'itained ap proximately constant in length (although of variable cross-section) during temper ature variations. Iha-ve found that in orderto 'ohtaln th s constant length of bubble when the-liquid employed is spirit the ,vol-

ume-o'f spiritand the voluin-eot air (1neas'- ured at normal atmospheric temperature of about 6QFahrenheit) shouldbe in the proportion of approximately seven parts of spirit "to three of air. have found that accurate results are ohtain ed wvith- 71% of spirit-(such as petroleum ether) to 29% of'air, but-thisproportion may obviously he departed" from ivithin limits it complete accuracy is not desired and moreover the proportion will differ somewhat with difierent liinds of spirit: It spirit and air in the'ahovementioned proportion are einployech a constant length of bubble can be obtained in levelhaving a circular bo re or :chamber, provided the level he made sufiieientl-y long (about 24 inehes for example)" and 0t suliiciently SiDalllOOn; (about half an'in-ch for example) to give an air bubble of smaller length than 'thelength ot' the level, but 'iuorder to, reduce the length of the level so as to conform to the practical.-requiren1ents tor surveying and other instruments, I may suitably modify the effective ,crosssection'al shape ot the bore or chamber of the level. i

.Inmorder-that the saidinvention may he clearly understoodand readily vcarried into reflect; thesame will noiv he described more fully with reference to; the accon'ipanying drawings, in wlnchs-w: Y

invention,

FigurejQ is, a V cross-section of Figure 1 and A 'is the body o'l the level, A the liquid therein and A? he air bubble.

Referring to Figures land 2, the level A is made of circular cross-section and the required proportio1 between the volume oi liquid and air is'ohtained by the insertion More specifically Figures?) and at are viewssimilar to Fin uites 1; and 2 showing another form of level,

1 Figure lis a sectional side.elevation shovn inc; one form 'ot'levelin' accordance with my ot a sealed tuhe B, (preferably made o'l'- glass) in the level A. This sealed tube might, if desired, be replaced by arod of corresponding size also preferably made of glass. The said sealed tube or rod may be only slightlyshorter than the level and is preferably unattached to the latter, while its weight is such that it sinks in the liquid and rests at the bottom of the level. The relative cross-sectional dimensions of the level and the said sealed tube or rod are such that there is a shallow body or waist of liquid betweenthe lower part of the bubble and the upper part of the sealed tube or rod as shown in Figure 9. i

In the construction shownby Figures 3 and l the sealed tube or rod of Figures 1 and 2 is dispensed with by making the level oi. the cross-sectional shape shown in Figure i. From this figure it will be seen that the lower wall of the level is fiat, the upper wall is of slightly curvedformation (i. e. it has a curvature of large radius) while the side walls have a curvature of small radius. If

desired the lower wall may be of similar curvature to the upper wall so as to give the level the form otan oval or ellipse the length otthe major (i. e. horizontal) axis of which materially exceeds the length of the minor (i. e. vertical) axis. Alternatively the lower wall may be curved upwards transversely.

It should be understood that where the term air is used throughout the specification and claims, there is meant any or vapor serving to form an indicating bubble. Furthermore, where the term .tube is used throughout the specification and claims, without further definition of itscharacter, is meant any form of; enclosure whatsoever, the term tube being used merely as defining an enclosing element whichconstitutes a housing for the spirit and the bubble. p

lVhat I claim and desire to secure by Letters Patent of the United States is 1. A spirit level with the usual bubble tube having the air and liquid therein in relative proportions adapted to maintain the length of the bubble substantially constant under temperature variations.

2. A spirit level with theusual bubble tube having the air and liquid therein in relative proportions adapted to maintain the length of the bubble substantially'constant under temperature variations, said tube "forming a spirit chamber with its upreverse per Wall curved transversely on a relatively ar 'e rec ius. 1 b l A spirit level with the usual bubble tube having therein the air and liquid in relative proportions adapted to maintain the stant under temperature variations, said tube forming a spirit chamber of flattened shape in cross section and with its upper 'wal'. curved transversely, on a relatively large radius.

5. A spirit level with the usual bubble tube having the liquid and air therein, when measured at normal atmospheric temperature, in the relative proportions of approxiiii-ate 1y 7 to 3, respectively. 6. A spirit level comprising the usual tube with an indicating bubble therein, said tube having the liquid and air,"when measured by volume at substantially normal atmospheric ten'iperature, in the relative proportions of approximately 7 to 3, respective ly, said tube having. a liquid chamber of flattened shape in cross section. I

7. A spirit level with. the .usualbubble tube having the liquid-and air therein, when measured by volume at normal atmospheric temperature, in the relative proportions of approximately 7 to 3, respectively, said tube forming a liquid chamber of flattened shape in cross section and with its upper wall curved transversely on a relatively large radius. 7 8. A spirit level with the usual bubble tube having the liquid and air therein, when measured at normal atmospheric temperature, in the relative proportions of approximately 7 to .3,'respective'.y, said tube forming a spirit chamberwith its upper wall curved transversely on a relatively large radius. V

9. In a spirit level, an elongated tube having its upper chamber. wall curved transversely on a relatively long radius, the Chi-111lber being relatively shallow in vertical planes and having its longer transverse axis in a horizontal plane.

SAMUEL VVE'STON. 

